In general, AWD increases the handling limit (traction limit) when you are on the throttle. However, that extra increase over RWD on pavement -- wet or dry, can only be exploited by drivers with very advanced skills (and on the streets, you need guts too.) Normal drivers can only take advantage of that on gravel, snow, or ice. No offense, but since you are asking this question, I think you fall into the latter for right now. BTW, welcome!
That extra traction does provide normal drivers with a little more safety, if he unknowingly exceeds what would be the limit of a RWD car. But that safety is now provided by VDC even on the RWD like Struan87 said. In fact, when both an AWD and a RWD car get beyond their limits, VDC works better for the RWD car as the current VDC technology stands.
Also, I actually think that the extra traction of the AWD provides people a false sense of security. Think about it, instead of feeling the fish tail on snow in the RWD, you will feel a safe and strong acceleration. But if that sense of security you get during acceleration causes you to drive faster, you will be surprised when it's time to brake, because AWD has ABSOLUTELY NO ADVANTAGE when it comes to braking.
So for your questions 2 and 3, my advices are firmly NO, NO. And for 4, I live in Michigan, and you can check my sig. to see what I bought. If you do get a snow, just go have some fun in an empty parking lot.[
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Good luck on your buying.
04 Sedan 6MT/Caribbean Blue/Willow/Aero/Sunroof/Bose/Free broken Infiniti pen